The invention concerns a rheometer having a measuring chamber which is limited or defined by a measuring chamber wall and in which at least one measuring part is disposed for acceptance of a sample, wherein the measuring chamber can have a flow-through gas brought to a control temperature by means of a temperature control device. The invention also concerns a method for temperature control of a rheometer sample disposed in a measurement chamber thereof, wherein the measurement chamber can have a gas flow temperature controlled by a temperature control device.
In order to determine rheological quantities of a sample it is necessary to a compressional or tensile force on and an associated deformation of the sample must be precisely measured with accurately defined ambient conditions. This is done e.g. using a rotational rheometer in which the sample is disposed between two plate-shaped, horizontally disposed measuring components. The measuring components are rotated relative to each other and the resulting reaction forces are measured. In order to minimize ambient influences during the measurement or in order to measure as a function of a predetermined temperature dependence, the measuring components as well as the sample are disposed in a measuring chamber in which the sample is shielding to as great an extent as possible relative to the surrounding environment.
In many applications, the sample must be kept at a predetermined temperature throughout the entire measurement or a predetermined temperature dependence must be followed, e.g. precise temperature control is required. By means of example, it is assumed below that the material sample must be kept at a temperature which is higher than that of the surrounding environment e.g. must be heated.
Conventional devices are provided for warming a gas, in particular air, using a temperature control device and to cause the warmed gas to flow through the measurement chamber until the sample is brought to a desired temperature. In order to keep the sample at this desired temperature throughout the entire measurement, the temperature controlled gas also flows through the measuring chamber during the measurement. This has, however, the associated disadvantage that the gas flows onto the measuring components as well as the sample and exercises a weak force on the measuring components which can falsify the measurement.
If, alternatively, one shuts off all gas flow during the measurement, the sample changes its temperature, since the environment, in particular to the measuring chamber wall, has a different temperature.
The underlying purpose of the invention is to provide a rheometer of the above mentioned kind, as well as a method for temperature control of its measurement chamber, with which a sample can be kept at a predetermined temperature or can follow a predetermined temperature dependence in a precise manner to facilitate accurate measurements at that temperature or during that temperature dependence.